Changes in Bone Mineral Density and Biomarkers of Bone Turnover with Calcium Supplementation During Initial Military Cadet Exercise Training

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ELIZABETH MCMILLAN WATSON
Changes in Bone Mineral Density and Biomarkers of Bone Turnover with Calcium Supplementation During Initial Military Cadet Exercise Training
(Under the direction of SHARON M. NICKOLS-RICHARDSON)
Osteoporosis is a condition involving decreased bone mineral density (BMD) and increased fragility of the skeletal system. Osteoporosis affects ~75 million individuals in the United States, Europe, and Japan. In the United States alone, hip fractures affect 500,000 individuals per year, and annual healthcare costs for osteoporotic fractures are approximately $14 billion. A high peak BMD can prevent or delay the onset of osteoporosis and its complications. Exercise and diet may affect peak BMD by as much as 20 to 40% each and have been identified as the two most important controllable factors determining BMD. The current study investigated the effect of a calcium, vitamin D, and vitamin K supplement combination during initial military cadet exercise training on: BMD, stress fracture occurrence, hormones associated with BMD, and biochemical markers of bone turnover. Significant changes in BMD, either between the supplemented group or the unsupplemented group or across time for both groups were not found. The majority of participants (n = 22) had unexpectedly high levels of physical activity prior to enrollment, and the initial military exercise training program included only moderate levels of activity. Therefore, the exercise stimulus to bone was likely insufficient to promote gains in BMD, regardless of the nutrient supplement status. Serum insulin-like growth factor-1 and osteocalcin significantly increased over time (p < 0.05 and p < 0.001, respectively), irrespective of treatment group. Significant decreases were found in dietary intake of calories (p < 0.01), carbohydrate (p < 0.05), protein (p < 0.0001), and fat (p < 0.01) over time. Decreases in reported dietary intake were likely due to less variety of foods eaten, and diminished compliance with food records. Significant differences were not found between groups or across time in dietary intakes of calcium, vitamin D, or vitamin K. Low dose supplementation with a calcium, vitamin D, vitamin K supplement during initial military training in young-adult cadets did not change BMD or alter stress fracture occurrence.